Burner control means



Dec. 10, 1963 w s w ETAL 3,113,610

BURNER CONTROL MEANS Filed Jan. 13, 1961 2 Sheets-Sheet 1 5O LUMENS/SQ FT.

10 LUMENSISQFT.

5 LUMENS/ SQ FT.

I (MILLIAMPS) 1 LUMEN/SQ.FT.

0 1O 2O 3O 4O 5O VOLTS H6. 1

W/L FRED AIGERT 8 A WYER A we 11A y 40/? G'ONFR Dec. 10, 1963 w. A. SAWYER ETAL 3, 3,

BURNER CONTROL MEANS Filed Jan. 15, 1961 2 Sheets-Sheet 2 *ONk THERMOSTAT FIG. 3

United States Patent 3,113,610 BURNER QONTRGL MEANS Wilfred A. Sawyer and David H. Surgeoner, Beaconsfield,

England, assignors to Satehwell Controls Limited,

Slough, England Filed Jan. 13, 1951, Ser. No. 82,423 Claims priority, application Great Britain Mar. 18, 1960 4 Claims. (Cl. 158-28) The present invention concerns improvements in burner control means and has more particularly as its object to provide an improved relay which may conveniently be associated with photo-sensitive means so as to provide an improved burner control means.

It is known that, in burner control means for use on fiuid fuel fired furnaces, means are normally provided to sense whether or not the flame is established and one very convenient form of such sensing means is a photosensitive cell. The arrangement is usually that the light from the flame falls upon the photo-sensitive cell and causes a current to flow in a control circuit and, after amplification if necessary, this current operates a relay which allows the burner to continue to run. The general arrangement is that unless the flame is established within a preset time after switching on, the control circuit is caused to go to lock-out unless there is illumination of the photo-sensitive cell which serves to prevent the control circuit going to lock-out. The disadvantage of this is that should the photo-sensitive cell be short circuited or otherwise damaged suflicient current may flow to prevent the control circuit going to lock-out when in point of fact flame is not established.

However, for any given type of photo-sensitive cell the current will be known to be within certain limits under normal conditions of operation whilst if the cell is short circuited the current will normally be much greater than that for normal operation.

Consequently, therefore, the present invention provides a relay device having three positions, namely off, normally energised and over-energised, the over-energised position of the relay serving to release a detent device preventing normal resetting of at least one of the contacts of the relay except by manual or like operation.

According to a further aspect of this invention there is provided burner control means comprising, in association with a photo-sensitive device, a relay wherein such relay has three positions, namely an oil? position, an energised position to which it is moved by the normal current fio. ing through the photo-sensitive device when the same is illuminated, and an over-energised position to which it is moved by a ctu'rent corresponding to a short circuit on the photo-sensitive device, all contacts controlled by such relay not resetting after over-energisation of the relay except upon manual or like operation.

Thus it will be understood that under normal no flame or flame conditions the relay will move between its oil and normally energised positions, but that should the photo-cell be damaged or short circuited the relay will go to the over-energised position from which it will not return normally. Thus a primary indication is given of failure conditions and very conveniently the over-energised position of the relay may be caused to close contacts energising a lock-out device such as is conventional in burner control systems. Manual resetting of the contacts is necessary and, of course, this term should be understood to mean resetting a solenoid or the like under manual control, but if the failure conditions persist the relay will immediately go again to the over-energised position.

In order that the invention may more readily be understood an embodiment of the same is now described with reference to the accompanying drawings, wherein:

3,113,610 Patented Dec. 10, 1963 FIGURE 1 is a graph of the characteristics of atypical photo-cell of the cadmium sulphide type,

FIGURE 2 illustrates the relay of the present invention, and

FIGURE 3 is a circuit diagram of a burner control means according to the invention and including the relay illustrated in FIGURE 2.

Referring to FIG. 1, the family of four curves A, B, C and D shows the current flow through a typical cadmium sulphide photo-cell as a function of the voltage applied directly to the cell for arbitrarily selected intensities of illumination of 50, 10, 5 and l lumen per square foot, respectively. The straight line FI-I extends between a point corresponding to an ordinate of 40 milliamperes at F and a point corresponding to an abscissa of 30 volts at H. The point F represents the maximum current of 40 milliarnperes which flows in a control circuit (described below) including a relay coil in series with the photo-cell when the photo-cell s short-circuited. The point H represents the open circuit voltage of the energizing source for the control circuit, which is 30' volts pulsating DC. and which is applied to the photo-cell when the photo-cell resistance becomes infinite.

The slope of the line FI-I corresponds to a resistance of 750 ohms for the relay coil, later to be described, neglecting the resistance of the wiring of the control circuit and the internal resistance of the 30 volt source.

For other coil resistances or source voltages, the line FH' must be redrawn accordingly with reference to the formula R I wherein R is the resistance of the control circuit exclusive of the photo-cell, E is the open circuit voltage of the source (point H), and I is the current which flows when the photo-cell is short-circuited (point F).

From these curves it is possible to read the current which will flow in the circuit for each of the four plotted intensities of illumination at the normal operating voltage of 30 volts, these current values being ascertainable from the intersections of the line FH with eachof the curves A, B, C or D. Thus in the case of the highest normal illumination the normal current will be 24 milli-amps whereas with minimum illumination it will be 4 milliamps.

The relay of the present invention is illustrated in FIG- URE 2 and comprises an operating coil 13 which is positioned to attract an armature 26 which is pivoted at a point 26a. The armature 26 is provided with an operator 26bwhich engages a movable contact 8. The relay is shown in the released position and in this position the contact 8 makes with a stationary contact 7. In the normal current energised position, the operator 26b .rnoves the contact 8 to break from the contact 7 and to make with a contact 25. This contact 25 is engaged by an operator 27 which is mounted upon an arm 28, the arm 28 being pivoted at a point 28a and being acted upon by a spring 2812 so as to be normally pressed against a fixed stop 29. It will be apparent that if the relay coil 13 is over-energised the operator 26b moving the contact 3 into engagement with the contact 25 will also move the operator 27 and swing the arm 28 about the pivot point 28a. This will cause the tail of the arm 28 to release a spring biased contact 18 which is normally held in engagement with a stationary contact 19' by the tail of the arm 28. In so releasing the contact 18 a circuit is, of course, broken but the end of the cont-act blade carrying the contact 18 will pass behind the arm 28 to prevent the resumption of the normal position, either by the arm 28 or by the contact 18.

FIGURE 3 includes certain elements of the relay described above with reference to FIGURE 2 and these elements are indicated in FIGURE 3 by the same reference numerals as are used in FIGURE 2. As shown in FIG- URE 3, an alternating current supply source is connected across a primary winding 9 of a transformer 10. Also connected across the current source is a motor M for supplying the fuel and an ignition transformer 6 these being in parallel with each other and in series with a contact 5 which is a contact of a motor relay to be described hereinafter.

A first secondary winding 11 is provided on the transformer 10 and supplies current to a photo-cell 12 which is in series with the relay coil 13, this relay coil being shunted by a half-wave rectifier B.

A second secondary winding is provided on the transformer 10 and is provided with end terminals 16 and 17 and with an intermediate tapping point 22. The terminal 16 is connected in series with the normally closed photocell relay overcurrent contacts 18, 19, a thermostat contact 20 and the motor relay coil 15 to the movable contact 8 of the photo-cell relay. A contact 7, with which the contact 8 makes in the oil position of the photo-cell relay, is connected in series with a lock-out time delay heater 21 and thence to the other transformer terminal 17 The contact 20 in FIGURE 3 represents the control contact and may, for example, be a thermostat. Thus on closing the contact 20 (the relay of FIGURE 2 being assumed to be unoperated) a circuit is set up through the contacts 18, 19, 20 to energise the motor relay coil 15 through the contacts 8, 7 and the heater 241 of a lockout delay device. Consequently the motor relay contact closes and the motor M and ignition transformer 6 are energised. The motor relay coil 15 also controls lock-in contacts 23, 24 which are connected in series between the tapping point 22 and the photo-cell relay contact 2.5. Under normal conditions, flame will be established and the photocell 12 will cause the relay coil 13 to be energised to break the contacts 8 and 7 and make the contacts 8 and 25. This has the effect of disconnecting the lock-out heater 211 from the circuit and establishing a self-locking circuit for the motor relay coil 15 through the motor relay contacts Q3, 24.

However, should there be a short circuit within or in the wiring leading to the photo-cell 12, the coil 13 will be over-energised as described and armature 26, in addition therefore to making the contacts 8 and 25 in its second position, will proceed to its third position wherein the contacts :18 and 19 will be locked open and the circuit including the motor relay coil 15 is broken and the contact 5 is opened.

It should be noted that in the description of FIGURE 3, only those parts necessarily associated with the relay of FIGURE 2 have been described.

Should flame not be established within a predetermined period, the heat generated in the heater 2d heats an actuator 2 1a sufficiently to cause that actuator to open the normally closed manually resettable safety contacts 21b and 21c, thereby de-energizing the motor :M and the ignition transformer 6 together with the transformer 10.

Should the electrical power fail during a run for such a short period that the flame does not become extinguished before power is restored, two undesirable conditions might arise if the self-locking motor relay contacts 23 and 24 were not provided.

*Firstly, the photo-cell controlled contact 8 may accidentally remain in engagement with contact 25 when the power fails so that, upon the restoration of power, the motor relay coil 15 would be reenergized and contact 5 would be reclosed, causing the burner to continue operation WVllEhOllt the protection afforded by the safety lock-out device controlled by the heater 21. The provision of the self-locking motor relay contacts 23 and 24, which open immediately the power fails, prevents this, the motor relay coil 15 remaining unenergized and motor control contact 5 remaining open as a consequence until the faulty operation of contact 8 is corrected.

Secondly, the contact 8 may break from contact 25 and make the con-tact 7 when power falls but as flame will still be present when power is restored these contacts revert to their run conditions immediately power is restored. Contact 5 would then be reclosed immediately power was restored and the burner would again continue operation without the protection afforded by the safety time delay lock-out device. The opening of self-locking contacts 23 and 24 immediately upon power failure prevents this and assures that flame can be reestablished only in the normal manner as descnibed above.

We claim:

1. 'In a burner control means, an electromagnetic relay including an operating coil and an armature, the armature assuming first, second and third positions in response to said coil being respectively unenergised, energised by a normal current and energised by a current in excess of normal; a photocell; a source of electrical power; circuit means including an electrically energised fuel supply means; first contact means in said circuit means operable to initially energise said fuel supply means when said armature is in said first position; second contact means in said circuit means operable to maintain energisation of said fuel supply means when said armature is in said second position; and third contact means in said circuit means operable in response to said armature assuming its third position to deenergise said fuel supply means; further circuit means connecting said coil and said photocell in series for energisation by said source, said photocell being adapted, when the burner is ignited, to pass said normal current; said fuel supply means being operative, when energised, to supply fuel to the burner.

2. A burner control means according to claim 1 further comprising resettable lockout means included in said relay and responsive to said armature assuming said third position, said lockout means maintaining said third contact means operated to deenergise said fuel supply means.

3. A burner control means according to claim 1 wherein further comprising thermostat means actuable to call for heat, said thermostat means being connected to control said first and second contact means for energizing said fuel supply means in response to said call for heat; and time delay means connected to decnergize said fuel control means independently of said third contact means in response to said armature remaining in said first position thereof for a time interval exceeding a predetermined maximum time interval after actuation of said thermostat means.

4. Burner control means comprising: a first electromagnetic relay including a first operating coil and an armature, said armature assuming first, second and third positions in response to said coil being respectively um energised, energised by a normal current and energised by a current in excess of normal; a photocell; a source of electrical power; first circuit means including an electrically energised fuel supply means; first contact means in said circuit means operable when said armature is in said first position; second contact means in said circuit means operable when said armature is in said second position; third contact means in said circuit means oper-able in response to said armature assuming its third position; second circuit means connecting said first operating coil and said photocell in series for energisation by said source, said photocell being adapted, when said burner is ignited, to pass said normal current through said first operating coil; a second electromagnetic relay having a second operating coil and first and second sets of normally open contacts, both sets of contacts being included in said first circuit means, said second operating coiling energisable through said first contact means to cause said first set of contacts to initially energise said fuel supply means, said second operating coil being further ener- References Cited in the file of this patent UNITED STATES PATENTS Miller-wise et a1. Nov. 23, 1954 Burcklmardt July 3, 1962 FOREIGN PATENTS Belgium June 29, 1957 

1. IN A BURNER CONTROL MEANS, AN ELECTROMAGNETIC RELAY INCLUDING AN OPERATING COIL AND AN ARMATURE, THE ARMATURE ASSUMING FIRST, SECOND AND THRID POSITIONS IN RESPONSE TO SAID COIL BEING RESPECTIVELY UNENERGISED, ENERGISED BY A NORMAL CURRENT AND ENERGISED BY A CURRENT IN EXCESS OF NORMAL; A PHOTOCELL; A SOURCE OF ELECTRICAL POWER; CIRCUIT MEANS INCLUDING AN ELECTRICALLY ENERGISED FUEL SUPPLY MEANS; FIRST CONTACT MEANS IN SAID CIRCUIT MEANS OPERABLE TO INITIALLY ENERGISE SAID FUEL SUPPLY MEANS WHEN SAID ARMATURE IS IN SAID FIRST POSITION; SECOND CONTACT MEANS IN SAID CIRCUIT MEANS OPERABLE TO MAINTAIN ENERGISATION OF SAID FUEL SUPPLY MEANS WHEN SAID ARMATURE IS IN SAID SECOND POSITION; AND THIRD CONTACT MEANS IN SAID CIRCUIT MEANS OPERABLE IN RESPONSE TO SAID ARMATURE ASSUMING ITS THIRD POSITION TO DEENERGISE SAID 